SNOW-2913796: [Local Testing] Add support for nullifzero function

What is the current behavior?

The nullifzero() function is not implemented in the Local Testing Framework. When we attempt to use this function with local_testing=True, they encounter the following error:

from snowflake.snowpark import Session
from snowflake.snowpark.functions import col, nullifzero

session = Session.builder.config("local_testing", True).create()
df = session.create_dataframe([[0], [1], [100]], schema=["value"])
result = df.select(nullifzero(col("value")))
result.show()

error:

NotImplementedError: [Local Testing] Function nullifzero is not implemented.
You can implement and make a patch by using the `snowflake.snowpark.mock.patch` decorator.

What is the desired behavior?

The nullifzero() function should work in Local Testing mode with the following behavior:

• When the input value is 0 (integer or float), return NULL
• When the input value is non-zero, return the original value
• Maintain the original data type while ensuring the result is nullable

This would match the behavior of Snowflake's NULLIFZERO SQL function.

If this is not an existing feature in snowflake-snowpark-python. How would this impact/improve non local testing mode?

This feature does not impact non-local testing mode. The nullifzero() function already works correctly when connected to Snowflake.

References, Other Background

#4036
I'm willing to implement this feature and submit a pull request. The implementation would include:

• mock_nullifzero function in src/snowflake/snowpark/mock/_functions.py
• test_nullifzero test case in tests/mock/test_functions.py